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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed
* with this work for additional information regarding copyright
* ownership. The ASF licenses this file to you under the Apache
* License, Version 2.0 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
* implied. See the License for the specific language governing
* permissions and limitations under the License.
*/
#ifndef APU_THREAD_POOL_H
#define APU_THREAD_POOL_H
#include "apu.h"
#include "apr_thread_proc.h"
/**
* @file apr_thread_pool.h
* @brief APR Thread Pool Library
* @remarks This library implements a thread pool using apr_thread_t. A thread
* pool is a set of threads that can be created in advance or on demand until a
* maximum number. When a task is scheduled, the thread pool will find an idle
* thread to handle the task. In case all existing threads are busy and the
* number of tasks in the queue is higher than the adjustable threshold, the
* pool will try to create a new thread to serve the task if the maximum number
* has not been reached. Otherwise, the task will be put into a queue based on
* priority, which can be valued from 0 to 255, with higher values being served
* first. If there are tasks with the same priority, the new task might be put at
* the top or at the bottom - it depends on which function is used to put the task.
*
* @remarks There may be the case where the thread pool can use up to the maximum
* number of threads at peak load, but having those threads idle afterwards. A
* maximum number of idle threads can be set so that the extra idling threads will
* be terminated to save system resources.
*/
#if APR_HAS_THREADS
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
/**
* @defgroup APR_Util_TP Thread Pool routines
* @ingroup APR_Util
* @{
*/
/** Opaque Thread Pool structure. */
typedef struct apr_thread_pool apr_thread_pool_t;
#define APR_THREAD_TASK_PRIORITY_LOWEST 0
#define APR_THREAD_TASK_PRIORITY_LOW 63
#define APR_THREAD_TASK_PRIORITY_NORMAL 127
#define APR_THREAD_TASK_PRIORITY_HIGH 191
#define APR_THREAD_TASK_PRIORITY_HIGHEST 255
/**
* Create a thread pool
* @param me The pointer in which to return the newly created apr_thread_pool
* object, or NULL if thread pool creation fails.
* @param init_threads The number of threads to be created initially, this number
* will also be used as the initial value for the maximum number of idle threads.
* @param max_threads The maximum number of threads that can be created
* @param pool The pool to use
* @return APR_SUCCESS if the thread pool was created successfully. Otherwise,
* the error code.
*/
APU_DECLARE(apr_status_t) apr_thread_pool_create(apr_thread_pool_t **me,
apr_size_t init_threads,
apr_size_t max_threads,
apr_pool_t *pool);
/**
* Destroy the thread pool and stop all the threads
* @return APR_SUCCESS if all threads are stopped.
*/
APU_DECLARE(apr_status_t) apr_thread_pool_destroy(apr_thread_pool_t *me);
/**
* Schedule a task to the bottom of the tasks of same priority.
* @param me The thread pool
* @param func The task function
* @param param The parameter for the task function
* @param priority The priority of the task.
* @param owner Owner of this task.
* @return APR_SUCCESS if the task had been scheduled successfully
*/
APU_DECLARE(apr_status_t) apr_thread_pool_push(apr_thread_pool_t *me,
apr_thread_start_t func,
void *param,
apr_byte_t priority,
void *owner);
/**
* Schedule a task to be run after a delay
* @param me The thread pool
* @param func The task function
* @param param The parameter for the task function
* @param time Time in microseconds
* @param owner Owner of this task.
* @return APR_SUCCESS if the task had been scheduled successfully
*/
APU_DECLARE(apr_status_t) apr_thread_pool_schedule(apr_thread_pool_t *me,
apr_thread_start_t func,
void *param,
apr_interval_time_t time,
void *owner);
/**
* Schedule a task to the top of the tasks of same priority.
* @param me The thread pool
* @param func The task function
* @param param The parameter for the task function
* @param priority The priority of the task.
* @param owner Owner of this task.
* @return APR_SUCCESS if the task had been scheduled successfully
*/
APU_DECLARE(apr_status_t) apr_thread_pool_top(apr_thread_pool_t *me,
apr_thread_start_t func,
void *param,
apr_byte_t priority,
void *owner);
/**
* Cancel tasks submitted by the owner. If there is any task from the owner that
* is currently running, the function will spin until the task finished.
* @param me The thread pool
* @param owner Owner of the task
* @return APR_SUCCESS if the task has been cancelled successfully
* @note The task function should not be calling cancel, otherwise the function
* may get stuck forever. The function assert if it detect such a case.
*/
APU_DECLARE(apr_status_t) apr_thread_pool_tasks_cancel(apr_thread_pool_t *me,
void *owner);
/**
* Get the current number of tasks waiting in the queue
* @param me The thread pool
* @return Number of tasks in the queue
*/
APU_DECLARE(apr_size_t) apr_thread_pool_tasks_count(apr_thread_pool_t *me);
/**
* Get the current number of scheduled tasks waiting in the queue
* @param me The thread pool
* @return Number of scheduled tasks in the queue
*/
APU_DECLARE(apr_size_t) apr_thread_pool_scheduled_tasks_count(apr_thread_pool_t *me);
/**
* Get the current number of threads
* @param me The thread pool
* @return Total number of threads
*/
APU_DECLARE(apr_size_t) apr_thread_pool_threads_count(apr_thread_pool_t *me);
/**
* Get the current number of busy threads
* @param me The thread pool
* @return Number of busy threads
*/
APU_DECLARE(apr_size_t) apr_thread_pool_busy_count(apr_thread_pool_t *me);
/**
* Get the current number of idle threads
* @param me The thread pool
* @return Number of idle threads
*/
APU_DECLARE(apr_size_t) apr_thread_pool_idle_count(apr_thread_pool_t *me);
/**
* Access function for the maximum number of idle threads. Number of current
* idle threads will be reduced to the new limit.
* @param me The thread pool
* @param cnt The number
* @return The number of threads that were stopped.
*/
APU_DECLARE(apr_size_t) apr_thread_pool_idle_max_set(apr_thread_pool_t *me,
apr_size_t cnt);
/**
* Get number of tasks that have run
* @param me The thread pool
* @return Number of tasks that have run
*/
APU_DECLARE(apr_size_t)
apr_thread_pool_tasks_run_count(apr_thread_pool_t * me);
/**
* Get high water mark of the number of tasks waiting to run
* @param me The thread pool
* @return High water mark of tasks waiting to run
*/
APU_DECLARE(apr_size_t)
apr_thread_pool_tasks_high_count(apr_thread_pool_t * me);
/**
* Get high water mark of the number of threads
* @param me The thread pool
* @return High water mark of threads in thread pool
*/
APU_DECLARE(apr_size_t)
apr_thread_pool_threads_high_count(apr_thread_pool_t * me);
/**
* Get the number of idle threads that were destroyed after timing out
* @param me The thread pool
* @return Number of idle threads that timed out
*/
APU_DECLARE(apr_size_t)
apr_thread_pool_threads_idle_timeout_count(apr_thread_pool_t * me);
/**
* Access function for the maximum number of idle threads
* @param me The thread pool
* @return The current maximum number
*/
APU_DECLARE(apr_size_t) apr_thread_pool_idle_max_get(apr_thread_pool_t *me);
/**
* Access function for the maximum number of threads.
* @param me The thread pool
* @param cnt Number of threads
* @return The original maximum number of threads
*/
APU_DECLARE(apr_size_t) apr_thread_pool_thread_max_set(apr_thread_pool_t *me,
apr_size_t cnt);
/**
* Access function for the maximum wait time (in microseconds) of an
* idling thread that exceeds the maximum number of idling threads.
* A non-zero value allows for the reaping of idling threads to shrink
* over time. Which helps reduce thrashing.
* @param me The thread pool
* @param timeout The number of microseconds an idle thread should wait
* till it reaps itself
* @return The original maximum wait time
*/
APU_DECLARE(apr_interval_time_t)
apr_thread_pool_idle_wait_set(apr_thread_pool_t * me,
apr_interval_time_t timeout);
/**
* Access function for the maximum wait time (in microseconds) of an
* idling thread that exceeds the maximum number of idling threads
* @param me The thread pool
* @return The current maximum wait time
*/
APU_DECLARE(apr_interval_time_t)
apr_thread_pool_idle_wait_get(apr_thread_pool_t * me);
/**
* Access function for the maximum number of threads
* @param me The thread pool
* @return The current maximum number
*/
APU_DECLARE(apr_size_t) apr_thread_pool_thread_max_get(apr_thread_pool_t *me);
/**
* Access function for the threshold of tasks in queue to trigger a new thread.
* @param me The thread pool
* @param cnt The new threshold
* @return The original threshold
*/
APU_DECLARE(apr_size_t) apr_thread_pool_threshold_set(apr_thread_pool_t *me,
apr_size_t val);
/**
* Access function for the threshold of tasks in queue to trigger a new thread.
* @param me The thread pool
* @return The current threshold
*/
APU_DECLARE(apr_size_t) apr_thread_pool_threshold_get(apr_thread_pool_t * me);
/**
* Get owner of the task currently been executed by the thread.
* @param thd The thread is executing a task
* @param owner Pointer to receive owner of the task.
* @return APR_SUCCESS if the owner is retrieved successfully
*/
APU_DECLARE(apr_status_t) apr_thread_pool_task_owner_get(apr_thread_t *thd,
void **owner);
/** @} */
#ifdef __cplusplus
}
#endif
#endif /* APR_HAS_THREADS */
#endif /* !APR_THREAD_POOL_H */
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